There are different types of output devices for material which is stored in large containers, which devices can be rotors, sliding frames, push floors etc. One kind of containers is silos, where the discharge is made by way of some kind of arrangement in the bottom of the silo for further working or transport of the material. The idea is that the material shall fall down by itself as the material is discharged from beneath, but this is sometimes not the case. Different materials have a tendency to stagnate, form bridges above the output device and along the walls of the silo, whereas less and less material is discharged.
DE 36 07 786 discloses an output device for a silo or a similar container with a circular cross section. The device comprises an arm fixed to a hub, to which a driving device is connected for rotation of the hub and the arm. In the bottom of the silo a circular discharge opening is arranged in the centre thereof. The arm is formed with a bending to force or press the material in the silo towards the centre and out through the discharge opening.
FIGS. 1A, 1B, and 1C show examples of some known output devices for containers with radial discharge opening. These are rotatably arranged on a centre axis and with a number of arms to shove the material so that it falls into a radial opening with conveying screws to carry the material out of the space. These known devices are either arranged with resilient arms, type 1 (hydraulic rotor) and 3 (hydraulic rotor), hydraulically and elastically respectively, or with fixed straight arms, type 2 (sliding star).
A great problem with these types of known output devices is that the direction of feed from the arms is directed towards the wall of the container and forwards. This concerns both the output devices with straight arms as well as resilient or pivotable arms, which at heavy resistance from the material are bent backwards in the direction of rotation. The design of the arms causes the material to be packed towards the walls of the container, and that a certain amount of material in the periphery of the container remains unmoved and that the material that is yet moved is pushed out to the unmoved material and a further compaction (collaring) of the material occurs. Thus, the amount of material being discharged from the discharge opening is not as large as desired, and the efficiency of the device decreases or even that the discharge is stopped.
Concerning straight arms, their design brings that packing towards the periphery can neither be prevented, nor that the compacted material can be disengaged/loosened because of the direction of movement/force directed outwards of these arms.
One drawback with the solution with fixed straight arms, except for the direction of feed, is that the arms in certain positions cover large parts of the discharge opening, which is to disadvantage of the continuity of the material supply into the opening. Thus, this also affects the efficiency of the device in a negative way.
Even a successive packing vertically can occur above the output device, at which an arch of packed material gradually is formed and the output device idles and the discharging stops (FIG. 2.).
The known output devices mentioned above, have a tendency to only bring together and/or try to force the material in certain directions—either towards other material or towards the walls or the like of the container—which brings evident tendencies of packing, and the devices tend to work against the falling down of the material to the discharge opening. This is a great problem at storing of materials that have a tendency to pack. Many containers also have a considerable volume, whereas any outer influence of the container to shake down material is not possible.